Glycosylation is important to the structures and functions of glycoproteins. For example, glycosylation is suggested to affect protein folding (and thus stability) and/or bioactivities of glycoproteins. The demand of therapeutic recombinant glycoproteins, especially monoclonal antibodies, robustly grows in the recent two decades. Previous studies reveal that minor differences in glycan structures of recombinant glycoproteins may impact on the biological activities and pharmacokinetics of the glycoproteins. For example, Darbepoetin alfa is a hyper-glycosylated analog of recombinant human erythropoietin (EPO) with two extra N-linked glycosylation sites. The extra N-glycosylation increases the percentage of the molecular mass in carbohydrates and significantly extends the serum half-life of Darbepoetin alfa, as compared to endogenous and recombinant EPO. In addition, for a therapeutic antibody whose efficacy mainly relies on antibody-dependent cell cytotoxicity (ADCC), both chemo-enzymatic and genetic approaches to remove the core fucose residue on the Fc portion have been developed to increase the potency of the ADCC effect induced by that antibody.
However, currently available methods for remodeling glycosylation often require multiple enzymes and/or multiple steps, resulting in high costs for manufacturing glyco-engineered recombinant proteins.